From: Daniel Wagner <dwagner@suse.de>
Date: Thu, 2 Sep 2021 11:20:02 +0200
Subject: nvme: avoid race in shutdown namespace removal
Patch-mainline: v5.15-rc2
Git-commit: 9edceaf43050f5ba1dd7d0011bcf68a736a17743
References: bsc#1188067
When we remove the siblings entry, we update ns->head->list, hence we
can't separate the removal and test for being empty. They have to be
in the same critical section to avoid a race.
To avoid breaking the refcounting imbalance again, add a list empty
check to nvme_find_ns_head.
Fixes: 5396fdac56d8 ("nvme: fix refcounting imbalance when all paths are down")
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/nvme/host/core.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3507,7 +3507,9 @@ static struct nvme_ns_head *nvme_find_ns
lockdep_assert_held(&subsys->lock);
list_for_each_entry(h, &subsys->nsheads, entry) {
- if (h->ns_id == nsid && kref_get_unless_zero(&h->ref))
+ if (h->ns_id != nsid)
+ continue;
+ if (!list_empty(&h->list) && kref_get_unless_zero(&h->ref))
return h;
}
@@ -3775,6 +3777,10 @@ static void nvme_ns_remove(struct nvme_n
mutex_lock(&ns->ctrl->subsys->lock);
list_del_rcu(&ns->siblings);
+ if (list_empty(&ns->head->list)) {
+ list_del_init(&ns->head->entry);
+ last_path = true;
+ }
mutex_unlock(&ns->ctrl->subsys->lock);
/* guarantee not available in head->list */
@@ -3795,13 +3801,6 @@ static void nvme_ns_remove(struct nvme_n
list_del_init(&ns->list);
up_write(&ns->ctrl->namespaces_rwsem);
- /* Synchronize with nvme_init_ns_head() */
- mutex_lock(&ns->head->subsys->lock);
- if (list_empty(&ns->head->list)) {
- list_del_init(&ns->head->entry);
- last_path = true;
- }
- mutex_unlock(&ns->head->subsys->lock);
if (last_path)
nvme_mpath_shutdown_disk(ns->head);
nvme_put_ns(ns);